Which marker is most characteristic for identifying plasma cells in flow cytometry?

Which marker is most characteristic for identifying plasma cells in flow cytometry?

• A. CD19
• B. CD45
• C. CD20
• D. CD38

Answer: (B)

In flow cytometry, identifying plasma cells is best done by looking at patterns of marker expression rather than a single label. Plasma cells typically have a distinctive CD45 expression level: it is dim compared with most other leukocytes, which usually show brighter CD45. This dim CD45 helps separate plasma cells from other cell types when you gate on CD45 intensity alongside scatter properties and other markers. Even though plasma cells often express high CD38 and sometimes CD138, those markers can be shared with other cell types, such as activated B cells or plasmablasts, making them less specific on their own. CD19 and CD20 are B-cell markers, but plasma cells can lose these markers, so they’re not reliable identifiers of mature plasma cells in many contexts. The relatively stable and distinguishable dim CD45 pattern therefore makes it the most informative single marker among the options for identifying plasma cells in flow cytometry.

In flow cytometry, identifying plasma cells is best done by looking at patterns of marker expression rather than a single label. Plasma cells typically have a distinctive CD45 expression level: it is dim compared with most other leukocytes, which usually show brighter CD45. This dim CD45 helps separate plasma cells from other cell types when you gate on CD45 intensity alongside scatter properties and other markers.

Even though plasma cells often express high CD38 and sometimes CD138, those markers can be shared with other cell types, such as activated B cells or plasmablasts, making them less specific on their own. CD19 and CD20 are B-cell markers, but plasma cells can lose these markers, so they’re not reliable identifiers of mature plasma cells in many contexts. The relatively stable and distinguishable dim CD45 pattern therefore makes it the most informative single marker among the options for identifying plasma cells in flow cytometry.